Transplantation-induced endothelial dysfunction as studied in rat aorta allografts

Background. Clinical evidence indicates that vascular endothelial cell (EC) dysfunction occurs early after transplantation (Tx) and initiates chronic graft vasculopathy. This study explored this phenomenon in rat aorta Tx using the stringent Dark Agouti (DA)-to-Lewis (LEW) and the weak Fischer 344 (F344)-to-LEW strain combinations. Methods. Donor abdominal aortae were orthotopically grafted into LEW rats. At post-Tx days 7, 14, 28, and 56, grafts were collected to assess changes in EC morphology (en face silver staining) and EC function, i.e., vasodilatory response to acetylcholine (ACH) after phenylephrine (PHE) precontraction; changes in vascular smooth muscle cell (VSMC alpha-actin (western blotting), degree of apoptosis (caspase-3 activity), and morphology. Results. In DA allografts, VSMC and EC dysfunctions developed concomitantly and were completed at 14 days post-Tx, most likely due to the EC and alpha-actinpositive VSMC loss. Meanwhile, allografts revealed markedly increased caspase-3 activity. Neointima formation, restricted to the edges of allografts at day 28, covered the entire allografts by day 56 post-Tx. In F344-allografts, VSMC function was maintained up to day 14 post-Tx, whereas ACH-induced relaxation was reduced by 50% at day 7 and abolished at day 14. EC denudation was not seen up to 56 days post-Tx, despite prominent leukocyte adhesion. Neointima formation was not detected at day 28 post-Tx but appeared along the entire allografts at day 56 post-Tx. Conclusions. These results confirm that Tx-induced EC dysfunction precedes the development of vasculopathy in rat aorta allografts and suggest that this early phenomenon can be best studied in the F344-to-LEW strain combination.